When site owners roll out emails to subscribers, they are not aware of how many subscribers actually opened their email and read it. Here to help find out these stats is a web service called CampaignCog.

CampaignCog is a free to use web service that helps you track your emails and various stats about them. Using the web tool you can start email campaigns and specify the number of subscribers for it. Next you select a start date and a merge tag that helps provide reports of each individual email you send. Finally you select whether or not the clicked links in your emails are tracked. With all this done, you are provided an HTML code that you should paste into your email or sending software.

This code helps track the email and gathers various stats such as how many subscribers opened your email, read it, skim-read it, forwarded it, or deleted it.